Injection Mold Having a Simplified Cooling System

ABSTRACT

An injection mold assembly for a high output consumer product injection molding machine, the injection mold assembly having a simplified cooling system. The simplified cooling system has a cooling complexity factor of less than three, preferably less than two, more preferably less than one.

TECHNICAL FIELD

The present invention relates to injection molds, more particularly, toinjection molds having a simplified cooling system.

BACKGROUND

Injection molding is a technology commonly used for high-volumemanufacturing of parts made of meltable material, most commonly of partsmade of thermoplastic polymers. During a repetitive injection moldingprocess, a plastic resin, most often in the form of small beads orpellets, is introduced to an injection molding machine that melts theresin beads under heat, pressure, and shear. Such resin can include amasterbatch material along with one or more colorants, additives,fillers, etc. The now molten resin is forcefully injected into a moldcavity having a particular cavity shape. The injected plastic is heldunder pressure in the mold cavity, cooled, and then removed as asolidified part having a shape that essentially duplicates the cavityshape of the mold. The mold itself may have a single cavity or multiplecavities. Each cavity may be connected to a flow channel by a gate,which directs the flow of the molten resin into the cavity. A moldedpart may have one or more gates. It is common for large parts to havetwo, three, or more gates to reduce the flow distance the polymer musttravel to fill the molded part. The one or multiple gates per cavity maybe located anywhere on the part geometry, and possess any cross-sectionshape such as being essentially circular or be shaped with an aspectratio of 1.1 or greater. Thus, a typical injection molding procedurecomprises four basic operations: (1) heating the plastic in theinjection molding machine to allow it to flow under pressure; (2)injecting the melted plastic into a mold cavity or cavities definedbetween two mold halves that have been closed; (3) allowing the plasticto cool and harden in the cavity or cavities while under pressure; and(4) opening the mold halves to allow the part to be ejected from themold.

The molten plastic resin is injected into the mold cavity and theplastic resin is forcibly pushed through the cavity by the injectionmolding machine until the plastic resin reaches the location in thecavity furthest from the gate. The resulting length and wall thicknessof the part is a result of the shape of the mold cavity.

The molds used in injection molding machines must be capable ofwithstanding these high melt pressures. Moreover, the material formingthe mold must have a fatigue limit that can withstand the maximum cyclicstress for the total number of cycles a mold is expected to run over thecourse of its lifetime. As a result, mold manufacturers typically formthe mold from materials having high hardness, such as tool steels,having greater than 30 Rc, and more often greater than 50 Rc. These highhardness materials are durable and equipped to withstand the highclamping pressures required to keep mold components pressed against oneanother during the plastic injection process. Additionally, these highhardness materials are better able to resist wear from the repeatedcontact between molding surfaces and polymer flow.

High production injection molding machines (i.e., class 101 and class102 molding machines) that produce thinwalled consumer productsexclusively use molds having a majority of the mold made from the highhardness materials. High production injection molding machines typicallyproduce 500,000 parts or more. Industrial quality production molds mustbe designed to produce at least 500,000 parts, preferably more than1,000,000 parts, more preferably more than 5,000,000 parts, and evenmore preferably more than 10,000,000 parts. These high productioninjection molding machines have multi cavity molds and complex coolingsystems to increase production rates. The high hardness materialsdescribed above are more capable of withstanding the repeated highpressure clamping and injection operations than lower hardnessmaterials. However, high hardness materials, such as most tool steels,have relatively low thermal conductivities, generally less than 20BTU/HR FT ° F., which leads to long cooling times as heat is transferredfrom the molten plastic material through the high hardness material to acooling fluid.

In an effort to reduce cycle times, typical high production injectionmolding machines having molds made of high hardness materials includerelatively complex internal cooling systems that circulate cooling fluidwithin the mold. These cooling systems accelerate cooling of the moldedparts, thus allowing the machine to complete more cycles in a givenamount of time, which increases production rates and thus the totalamount of molded parts produced. However, these cooling systems addcomplexity and cost to the injection molds. In some class 101 molds morethan 1 or 2 million parts may be produced, these molds are sometimesreferred to as “ultra high productivity molds” Class 101 molds that runin 400 ton or larger presses are sometimes referred to as “400 class”molds within the industry.

High hardness materials are generally fairly difficult to machine. As aresult, known high throughput injection molds require extensivemachining time and expensive machining equipment to form, and expensiveand time consuming post-machining steps to relieve stresses and optimizematerial hardness. Milling and/or forming cooling channels within thesecomplex molds adds even more time and costs to the manufacture oftypical high throughput injection molds.

There is a tradeoff between machining complexity and cooling efficiencyin traditional, high hardness molds. Ideally, cooling channels should bemachined as close to the mold cavity surfaces as possible. Additionally,conformal cooling is desirable and most effective. However, machiningconformal cooling channels close to molding surfaces is difficult, timeconsuming, and expensive. Generally, machining cooling channels withinabout 5 mm of the mold surfaces is considered to be the practical limit.This practical limit reduces cooling efficiency due to material betweenthe cooling fluid and the hot plastic having low thermal conductivity.Conventional machining techniques, along with conventional moldmaterials (i.e., high hardness and low thermal conductivity) place alower limit on cycle time and cooling efficiency for a given mold.

Furthermore, locating cooling lines close to the mold surfaces requiresprecise machining of the cooling lines in the molds. Because the moldsare attached to support plates when placed in a clamping device of theinjection molding machine, fluid seals must be located where the coolinglines transition from the support plate to the mold (because the fluidcirculating systems (e.g., pumps) must be located outside of the molds).These fluid seals may fail, causing cooling fluid to escape. As aresult, parts may be incompletely cooled, which produces an inferiorpart, or the plastic in the mold may be contaminated with cooling fluid,which is also undesirable.

Still further, practical limitations on machining cooling channelsresults in unequal cooling within the mold. As a result, temperaturegradients are produced within the mold cavity. Often the temperature ofthe surface of a mold cavity can vary by ten degrees Celsius or more.This wide variation in temperature within the mold can lead toimperfections in the molded parts.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrativeembodiments can be understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 illustrates a schematic view of an injection molding machineconstructed according to the disclosure;

FIG. 2 illustrates one embodiment of a thin-walled part formed in theinjection molding machine of FIG. 1;

FIG. 3 is a cavity pressure vs. time graph for a mold cavity in a moldof the injection molding machine of FIG. 1;

FIG. 4 is a cross-sectional view of one embodiment of a mold assembly ofthe injection molding machine of FIG. 1;

FIGS. 5A-5E illustrate different views of various mold assemblies havinga plurality of cooling lines machined in a support plate;

FIG. 6 illustrates a cross-sectional view of a mold assembly having aplurality of cooling lines machined in a support plate that extend intoa mold side ;

FIG. 7 illustrates a close-up sectional view of a cooling line includinga baffle;

FIG. 8 illustrates a perspective cross-sectional view of a mold assemblyincluding a plurality of cooling lines machined along at least twodifferent axes;

FIG. 9 illustrates a perspective cross-sectional view of a mold assemblyhaving a plurality of terminal cooling lines and a plurality of throughbore cooling lines machined along at least two different machining axes;

FIG. 10 illustrates a perspective partially transparent view of a moldassembly having a plurality of cooling lines, at least one of thecooling lines being formed by two terminal cooling lines that join oneanother at terminal ends to form a non-terminal cooling line, eachterminal cooling line being machined along a different machining axis;

FIG. 11 illustrates a perspective view of a mold assembly having anactively cooled dynamic part;

FIG. 12 illustrates a perspective view of a mold assembly having atleast one cooling line that includes non-linear, non-coaxial, ornon-planar cooling channel; and

FIG. 13 illustrates one embodiment of a cube mold that incorporates amold having a simplified cooling system.

DETAILED DESCRIPTION

Embodiments of the present invention generally relate to systems,machines, products, and methods of producing products by injectionmolding and more specifically to systems, products, and methods ofproducing products by low constant pressure injection molding.

The term “low pressure” as used herein with respect to melt pressure ofa thermoplastic material, means melt pressures in a vicinity of a nozzleof an injection molding machine of 6000 psi and lower.

The term “substantially constant pressure” as used herein with respectto a melt pressure of a thermoplastic material, means that deviationsfrom a baseline melt pressure do not produce meaningful changes inphysical properties of the thermoplastic material. For example,“substantially constant pressure” includes, but is not limited to,pressure variations for which viscosity of the melted thermoplasticmaterial do not meaningfully change. The term “substantially constant”in this respect includes deviations of approximately 30% from a baselinemelt pressure. For example, the term “a substantially constant pressureof approximately 4600 psi” includes pressure fluctuations within therange of about 6000 psi (30% above 4600 psi) to about 3200 psi (30%below 4600 psi). A melt pressure is considered substantially constant aslong as the melt pressure fluctuates no more than 30% from the recitedpressure.

Referring to the figures in detail, FIG. 1 illustrates an exemplary lowconstant pressure injection molding apparatus 10 for producingthin-walled parts in high volumes (e.g., a class 101 or 102 injectionmold, or an “ultra high productivity mold”). The injection moldingapparatus 10 generally includes an injection system 12 and a clampingsystem 14. A thermoplastic material may be introduced to the injectionsystem 12 in the form of thermoplastic pellets 16. The thermoplasticpellets 16 may be placed into a hopper 18, which feeds the thermoplasticpellets 16 into a heated barrel 20 of the injection system 12. Thethermoplastic pellets 16, after being fed into the heated barrel 20, maybe driven to the end of the heated barrel 20 by a reciprocating screw22. The heating of the heated barrel 20 and the compression of thethermoplastic pellets 16 by the reciprocating screw 22 causes thethermoplastic pellets 16 to melt, forming a molten thermoplasticmaterial 24. The molten thermoplastic material is typically processed ata temperature of about 130° C. to about 410° C.

The reciprocating screw 22 forces the molten thermoplastic material 24,toward a nozzle 26 to form a shot of thermoplastic material, which willbe injected into a mold cavity 32 of a mold 28. The molten thermoplasticmaterial 24 may be injected through a gate 30, which directs the flow ofthe molten thermoplastic material 24 to the mold cavity 32. The moldcavity 32 is formed between first and second mold parts 25, 27 of themold 28 and the first and second mold parts 25, 27 are held togetherunder pressure by a press or clamping unit 34. The press or clampingunit 34 applies a clamping force that needs to be greater than the forceexerted by the injection pressure acting to separate the two mold halvesto hold the first and second mold parts 25, 27 together while the moltenthermoplastic material 24 is injected into the mold cavity 32. Tosupport these clamping forces, the clamping system 14 may include a moldframe and a mold base, the mold frame and the mold base being formedfrom a material having a surface hardness of more than about 165 BHN andpreferably less than 260 BHN, although materials having surface hardnessBHN values of greater than 260 may be used as long as the material iseasily machineable, as discussed further below.

Once the shot of molten thermoplastic material 24 is injected into themold cavity 32, the reciprocating screw 22 stops traveling forward. Themolten thermoplastic material 24 takes the form of the mold cavity 32and the molten thermoplastic material 24 cools inside the mold 28 untilthe thermoplastic material 24 solidifies. Once the thermoplasticmaterial 24 has solidified, the press 34 releases the first and secondmold parts 25, 27, the first and second mold parts 25, 27 are separatedfrom one another, and the finished part may be ejected from the mold 28.The mold 28 may include a plurality of mold cavities 32 to increaseoverall production rates. The shapes of the cavities of the plurality ofmold cavities may be identical, similar or different from each other.(The latter may be considered a family of mold cavities).

A controller 50 is communicatively connected with a sensor 52 and ascrew control 36. The controller 50 may include a microprocessor, amemory, and one or more communication links. The controller 50 may beconnected to the sensor 52 and the screw control 36 via wiredconnections 54, 56, respectively. In other embodiments, the controller50 may be connected to the sensor 52 and screw control 56 via a wirelessconnection, a mechanical connection, a hydraulic connection, a pneumaticconnection, or any other type of communication connection known to thosehaving ordinary skill in the art that will allow the controller 50 tocommunicate with both the sensor 52 and the screw control 36.

In the embodiment of FIG. 1, the sensor 52 is a pressure sensor thatmeasures (directly or indirectly) melt pressure of the moltenthermoplastic material 24 in the nozzle 26. The sensor 52 generates anelectrical signal that is transmitted to the controller 50. Thecontroller 50 then commands the screw control 36 to advance the screw 22at a rate that maintains a substantially constant melt pressure of themolten thermoplastic material 24 in the nozzle 26. While the sensor 52may directly measure the melt pressure, the sensor 52 may measure othercharacteristics of the molten thermoplastic material 24, such astemperature, viscosity, flow rate, etc, that are indicative of meltpressure. Likewise, the sensor 52 need not be located directly in thenozzle 26, but rather the sensor 52 may be located at any locationwithin the injection system 12 or mold 28 that is fluidly connected withthe nozzle 26. The sensor 52 need not be in direct contact with theinjected fluid and may alternatively be in dynamic communication withthe fluid and able to sense the pressure of the fluid and/or other fluidcharacteristics. If the sensor 52 is not located within the nozzle 26,appropriate correction factors may be applied to the measuredcharacteristic to calculate the melt pressure in the nozzle 26. In yetother embodiments, the sensor 52 need not be disposed at a locationwhich is fluidly connected with the nozzle. Rather, the sensor couldmeasure clamping force generated by the clamping system 14 at a moldparting line between the first and second mold parts 25, 27. In oneaspect the controller 50 may maintain the pressure according to theinput from sensor 52.

Although an active, closed loop controller 50 is illustrated in FIG. 1,other pressure regulating devices may be used instead of the closed loopcontroller 50. For example, a pressure regulating valve (not shown) or apressure relief valve (not shown) may replace the controller 50 toregulate the melt pressure of the molten thermoplastic material 24. Morespecifically, the pressure regulating valve and pressure relief valvecan prevent overpressurization of the mold 28. Another alternativemechanism for preventing overpressurization of the mold 28 is an alarmthat is activated when an overpressurization condition is detected.

Turning now to FIG. 2, an example molded part 100 is illustrated. Themolded part 100 is a thin-walled part. Molded parts are generallyconsidered to be thin-walled when a length of a flow channel L dividedby a thickness of the flow channel T is greater than 100 (i.e.,L/T>100). The low constant pressure injection molding systems and moldshaving simplified cooling that are described herein become increasinglyadvantageous for molding parts as L/T ratios increase, particularly forparts having L/T>200, or L/T>250 because the molten thermoplasticmaterial includes a continuous flow front that advances through the moldcavity, which fills the mold cavity with thermoplastic material moreconsistently than high variable pressure injection molding systems. Thelength of the flow channel L is measured from a gate 102 to a flowchannel end 104. Thin-walled parts are especially prevalent in theconsumer products industry and healthcare or medical supplies industry.

For mold cavities having a more complicated geometry, the L/T ratio maybe calculated by integrating the T dimension over the length of the moldcavity 32 from a gate 102 to the end of the mold cavity 32, anddetermining the longest length of flow from the gate 102 to the end ofthe mold cavity 32. The L/T ratio can then be determined by dividing thelongest length of flow by the average part thickness. In the case wherea mold cavity 32 has more than one gate 30, the L/T ratio is determinedby integrating L and T for the portion of the mold cavity 32 filled byeach individual gate and the overall L/T ratio for a given mold cavityis the highest L/T ratio that is calculated for any of the gates.

Thin-walled parts present certain obstacles in injection molding. Forexample, the thinness of the flow channel tends to cool the moltenthermoplastic material before the material reaches the flow channel end104. When this happens, the thermoplastic material freezes off and nolonger flows, which results in an incomplete part. To overcome thisproblem, traditional injection molding machines inject the moltenthermoplastic material into the mold at very high pressures, typicallygreater than 15,000 psi, so that the molten thermoplastic materialrapidly fills the mold cavity before having a chance to cool and freezeoff. This is one reason that manufacturers of the thermoplasticmaterials teach injecting at very high pressures. Another reasontraditional injection molding machines inject molten plastic into themold at high pressures is the increased shear, which increases flowcharacteristics, as discussed above. These very high injection pressuresrequire the use of very hard materials to form the mold 28 and the feedsystem.

Traditional injection molding machines use molds made of tool steels orother hard materials to make the mold. While these tool steels arerobust enough to withstand the very high injection pressures, toolsteels are relatively poor thermal conductors. As a result, very complexcooling systems are machined into the molds to enhance cooling timeswhen the mold cavity is filled, which reduces cycle times and increasesproductivity of the mold. However, these very complex cooling systemsadd great time and expense to the mold making process.

The inventors have discovered that shear-thinning thermoplastics (evenminimally shear- thinning thermoplastics) may be injected into the mold28 at low, substantially constant, pressure without any significantadverse affects. Examples of these materials include but are not limitedto polymers and copolymers comprised of, polyolefins (e.g.,polypropylene, polyethylene), thermoplastic elastomers, polyesters (e.g.polyethelyne terephthalate, polybutelene terephthalate), polystyrene,polyethylene furanoate (PEF), polycarbonate,poly(acrylonitrile-butadiene-styrene), poly(latic acid),polyhydroxyalkanoate, polyamides, polyacetals, ethylene-alpha olefinrubbers, and styrene-butadiene-stryene block copolymers. In fact, partsmolded at low, substantially constant, pressures exhibit some superiorproperties as compared to the same part molded at a conventional highpressure. This discovery directly contradicts conventional wisdom withinthe industry that teaches higher injection pressures are better. Withoutbeing bound by theory, it is believed that injecting the moltenthermoplastic material into the mold 28 at low, substantially constant,pressures creates a continuous flow front of thermoplastic material thatadvances through the mold from a gate to a farthest part of the moldcavity. By maintaining a low level of shear, the thermoplastic materialremains liquid and flowable at much lower temperatures and pressuresthan is otherwise believed to be possible in conventional high pressureinjection molding systems.

Turning now to FIG. 3, a typical pressure-time curve for a conventionalhigh pressure injection molding process is illustrated by the dashedline 200. By contrast, a pressure-time curve for the disclosed lowconstant pressure injection molding machine is illustrated by the solidline 210.

In the conventional case, melt pressure is rapidly increased to wellover 15,000 psi and then held at a relatively high pressure, more than15,000 psi, for a first period of time 220. The first period of time 220is the fill time in which molten plastic material flows into the moldcavity. Thereafter, the melt pressure is decreased and held at a lower,but still relatively high pressure, 10,000 psi or more, for a secondperiod of time 230. The second period of time 230 is a packing time inwhich the melt pressure is maintained to ensure that all gaps in themold cavity are back filled. The mold cavity in a conventional highpressure injection molding system is filled from the end of the flowchannel back to towards the gate. As a result, plastic in various stagesof solidification are packed upon one another, which may causeinconsistencies in the finished product, as discussed above. Moreover,the conventional packing of plastic in various stages of solidificationresults in some non-ideal material properties, for example, molded-instresses, sink, and non-optimal optical properties.

The constant low pressure injection molding system, on the other hand,injects the molten plastic material into the mold cavity at asubstantially constant low pressure for a single time period 240. Theinjection pressure is less than 6,000 psi. By using a substantiallyconstant low pressure, the molten thermoplastic material maintains acontinuous melt front that advances through the flow channel from thegate towards the end of the flow channel. Thus, the plastic materialremains relatively uniform at any point along the flow channel, whichresults in a more uniform and consistent finished product. By fillingthe mold with a relatively uniform plastic material, the finished moldedparts may form crystalline structures that have better mechanical and/orbetter optical properties than conventionally molded parts. Amorphouspolymers may also form structures having superior mechanical and/oroptical properties. Moreover, the skin layers of parts molded at lowconstant pressures exhibit different characteristics than skin layers ofconventionally molded parts. As a result, the skin layers of partsmolded under low constant pressure can have better optical propertiesthan skin layers of conventionally molded parts.

By maintaining a substantially constant and low (e.g., less than 6000psi) melt pressure within the nozzle, more machineable materials may beused to form the mold 28. For example, the mold 28 illustrated in FIG. 1may be formed of a material having a milling machining index of greaterthan 100% (such as 100-1000%, 100-900%, 100-800%, 100-700%, 100-600%,100-500%, 100-400%, 100-300%, 100-250%, 100-225%, 100-200%, 100-180%,100-160%, 100-150%, 100-140%, 100-130%, 100-120%, 100-110%, 120-250%,120-225%, 120-200%, 120-180%, 120-160%, 120-150%, 120-140%, 120-130%,140-400%, 150-300%, 160-250%, or 180-225%, or any other range formed byany of these values for percentage), a drilling machining index ofgreater than 100%, (such as 100-1000%, 100-900%, 100-800%, 100-700%,100-600%, 100-500%, 100-400%, 100-300%, 100-250%, 100-225%, 100-200%,100-180%, 100-160%, 100-150%, 100-140%, 100-130%, 100-120%, 100-110%,120-250%, 120-225%, 120-200%, 120-180%, 120-160%, 120-150%, 120-140%,120-130%, 140-400%, 150-300%, 160-250%, or 180-225%, or any other rangeformed by any of these values for percentage), a drilling machiningindex of greater than 100% (such as 100-1000%, 100-900%, 100-800%,100-700%, 100-600%, 100-500%, 100-400%, 100-300%, 100-250%, 100-225%,100-200%, 100-180%, 100-160%, 100-150%, 100-140%, 100-130%, 100-120%,100-110%, 120-250%, 120-225%, 120-200%, 120-180%, 120-160%, 120-150%,120-140%, 120-130%, 140-400%, 150-300%, 160-250%, or 180-225%, or anyother range formed by any of these values for percentage), a wire EDMmachining index of greater than 100% (such as 100-1000%, 100-900%,100-800%, 100-700%, 100-600%, 100-500%, 100-400%, 100-300%, 100-250%,100-225%, 100-200%, 100-180%, 100-160%, 100-150%, 100-140%, 100-130%,100-120%, 100-110%, 120-250%, 120-225%, 120-200%, 120-180%, 120-160%,120-150%, 120-140%, 120-130%, 140-400%, 150-300%, 160-250%, or 180-225%,or any other range formed by any of these values for percentage), agraphite sinker EDM machining index of greater than 200% % (such as200-1000%, 200-900%, 200-800%, 200-700%, 200-600%, 200-500%, 200-400%,200-300%, 200-250%, 300-900%, 300-800%, 300-700%, 300-600%, 300-500%,400-800%, 400-700%, 400-600%, 400-500%, or any other range formed by anyof these values for percentage), or a copper sinker EDM machining indexof greater than 150% (such as 150-1000%, 150-900%, 150-800%, 150-700%,150-600%, 150-500%, 150-400%, 150-300%, 150-250%, 150-225%, 150-200%,150-175%, 250-800%, 250-700%, 250-600%, 250-500%, 250-400%, 250-300%, orany other range formed by any of these values for percentage). Themachining indexes are based upon milling, drilling, wire EDM, and sinkerEDM tests of various materials. The test methods for determining themachining indices are explained in more detail below. Examples ofmachining indexes for a sample of materials is compiled below in Table1.

TABLE 1 Milling Drilling Spindle Spindle Wire EDM Sinker EDM-GraphiteSinker EDM-Copper Material 12129D Load Index % Load Index % time Index %time Index % time Index % 1117* 0.72 100% 0.32 100% 9:34 100% 0:14:48100% 0:24:00 100% 6061 Al 0.50 144% 0.20 160% 4:46 201% 0:05:58 248%0:15:36 154% 7075 Al 0.55 131% 0.24 133% 4:48 199% 0:05:20 278% 0:12:27193% Alcoa QC-10 Al 0.56 129% 0.24 133% 4:47 200% 0:05:11 286% 0:12:21194% 4140 0.92  78% 0.37  86% 9:28 101% 0:09:36 154% 0:19:20 124% 420 SS1.36  53% 0.39  82% 8:30 113% 0:10:12 145% 0:23:20 103% A2 0.97  74%0.45  71% 8:52 108% 0:08:00 185% 0:20:12 119% S7 1.20  60% 0.43  74%9:03 106% 0:12:53 115% 0:20:58 114% P20 1.10  65% 0.38  84% 9:26 101%0:11:47 126% 0:20:30 117% PX5 1.12  64% 0.37  86% 9:22 102% 0:12:37 117%0:23:18 103% Moldmax HH 0.80  90% 0.36  89% 6:00 159% 6:59:35  4% 10:43:38  55% 3 Ampcoloy 944 0.62 116% 0.32 100% 6:53 139% 3:13:41  8% 20:30:21  79% 4 *1117 is the benchmark material for this test. Publisheddata references 1212 carbon steel as the benchmark material. 1212 wasnot readily available. Of the published data, 1117 was the closest incomposition and machining index percentage (91%). 1 Significant graphiteelectrode wear: ~20% 2 graphite electrode wear: ~15% 3 Cu electrodewear: ~15% 4 Cu electrode wear: ~3%

Using easily machineable materials to form the mold 28 results ingreatly decreased manufacturing time and thus, a decrease inmanufacturing costs. Moreover, these machineable materials generallyhave better thermal conductivity than tool steels, which increasescooling efficiency and decreases the need for complex cooling systems.

When forming the mold 28 of these easily machineable materials, it isalso advantageous to select easily machineable materials having goodthermal conductivity properties. Materials having thermal conductivitiesof more than 30 BTU/HR FT ° F. are particularly advantageous. Inparticular, these materials can have thermal conductivities (measured inBTU/HR FT ° F.) of 30-200, 30-180, 30-160, 30-140, 30-120, 30-100,30-80, 30-60, 30-40, 40-200, 60-200, 80-200, 100-200, 120-200, 140-200,160-200, 180-200, 40-200, 40-180, 40-160, 40-140, 40-120, 40-100, 40-80,40-60, 50-140, 60-140, 70-140, 80-140, 90-140, 100-140, 110-140,120-140, 50-130, 50-120, 50-110, 50-100, 50-90, 50-80, 50-70, 50-60,60-130, 70-130, 80-130, 90-130, 100-130, 110-130, 120-130, 60-120,60-110, 60-100, 60-90, 60-80, 60-70, 70-130, 70-120, 70-110, 70-100,70-90, 70-80, 70-110, 70-100, 70-90, 70-80, 80-120, 80-110, 80-100, or80-90, or any other range formed by any of these values for thermalconductivity. For example easily machineable materials having goodthermal conductivities include, but are not limited to, QC-10 (availablefrom Alco), Alumold 500 (available from Alcan), Duramold-5 (availablefrom Vista Metals, Corp.) and Hokotol (available from Aleris). Materialswith good thermal conductivity more efficiently transmit heat from thethermoplastic material out of the mold. As a result, more simple coolingsystems may be used.

One example of a multi-cavity mold assembly 28 is illustrated in FIG. 4.Multi-cavity molds generally include a feed manifold 60 that directsmolten thermoplastic material from the nozzle 26 to the individual moldcavities 32. The feed manifold 60 includes a sprue 62, which directs themolten thermoplastic material into one or more runners or feed channels64. Each runner 64 may feed multiple mold cavities 32. High productivitymolds may include four or more mold cavities 32, sometimes as many asthree hundred and eighty four mold cavities 32, and often also mayinclude heated runners 64. Some embodiments of constant low pressureinjecting molding machines may include non-naturally balanced feedsystems, such as artificially balanced feed systems, or non-balancedfeed systems.

Drilling and Milling Machineability Index Test Methods

The drilling and milling machineability indices listed above in Table 1were determined by testing the representative materials in carefullycontrolled test methods, which are described below.

The machineability index for each material was determined by measuringthe spindle load needed to drill or mill a piece of the material withall other machine conditions (e.g., machine table feed rate, spindlerpm, etc.) being held constant between the various materials. Spindleload is reported as a ratio of the measured spindle load to the maximumspindle torque load of 75 ft-lb at 1400 rpm for the drilling or millingdevice. The index percentage was calculated as a ratio between thespindle load for 1117 steel to the spindle load for the test material.

The test milling or drilling machine was a Haas VF-3 Machining Center.

TABLE 2 Drilling Conditions Spot Drill 118 degree 0.5″ diameter, drilledto 0.0693″ depth Drill Bit 15/32″ diameter high speed steel uncoatedjobber length bit Spindle Speed 1200 rpm Depth of Drill 0.5″ Drill Rate3 in/min Other No chip break routine used

TABLE 3 Milling Conditions Mill 0.5″ diameter 4 flute carbide flatbottom end mill, uncoated (SGS part # 36432 www.sgstool.com) SpindleSpeed 1200 rpm Depth of Cut 0.5″ Stock Feed Rate 20 in/min

For all tests “flood blast” cooling was used. The coolant was Koolrite2290.

EDM Machineability Index Test Methods

The graphite and copper sinker EDM machineability indices listed abovein Table 1 were determined by testing the representative materials in acarefully controlled test method, which is described below.

The EDM machineability index for the various materials were determinedby measuring the time to burn an area (specifics below) into the varioustest metals. The machineability index percentage was calculated as theratio of the time to burn into 1117 steel to time required to burn thesame area into the other test materials.

TABLE 4 Wire EDM Equipment Fanuc OB Wire 0.25 mm diameter hard brass Cut1″ thick × 1″ length (1 sq. ″) Parameters Used Fanuc on board artificialintelligence, override at 100%

TABLE 5 Sinker EDM-Graphite Equipment Ingersoll Gantry 800 withMitsubishi EX Controller Wire System 3R pre-mounted 25 mm diameter PocoEDM 3 graphite Cut 0.1″ Z axis plunge Parameters Used Mitsubishi CNCcontrols with FAP EX Series Technology

TABLE 6 Sinker EDM-Copper Equipment Ingersoll Gantry 800 with MitsubishiEX Controller Wire System 3R pre-mounted 25 mm diameter Tellurium CopperCut 0.1″ Z axis plunge Parameters Used Mitsubishi CNC controls with FAPEX Series Technology

The disclosed low constant pressure injection molding machinesadvantageously employ molds constructed from easily machineablematerials. As a result, the disclosed low constant pressure injectionmolds (and thus the disclosed low constant pressure injection moldingmachines) are less expensive and faster to produce. Additionally, thedisclosed low constant pressure injection molding machines are capableof employing more flexible support structures and more adaptabledelivery structures, such as wider platen widths, increased tie barspacing, elimination of tie bars, lighter weight construction tofacilitate faster movements, and non- naturally balanced feed systems.Thus, the disclosed low constant pressure injection molding machines maybe modified to fit delivery needs and are more easily customizable forparticular molded parts.

Moreover, the disclosed low constant pressure injection molds (e.g.,mold assemblies that include one or more mold sides and one or moresupport plates) may include simplified cooling systems relative tocooling systems found in conventional high pressure injection molds. Thesimplified cooling systems are more economical than conventional coolingsystems because the simplified cooling systems are more quickly andeasily produced. Additionally, the simplified cooling systems use lesscoolant, which further reduces cooling costs during molding operations.In some cases, the simplified cooling systems may be located solely inthe mold support plates, which allows the molds to be changed withoutthe need for changing the cooling system. In summary, the simplifiedcooling systems of the disclosed low constant pressure injection moldingmolds are more economical than conventional complex cooling systemsfound in conventional high pressure injection molds.

Cooling systems of all sorts may be categorized in a system of coolingcomplexity levels, with cooling complexity level zero representing themost simple cooling system and higher cooling complexity levelsrepresenting progressively more complex cooling systems. This system ofcooling system categorization is discussed below in more detail.However, conventional high productivity consumer product injectionmolding machines (e.g., class 101 and 102 molding machines) employcomplex cooling systems to reduce cycle time and improve productivity.Generally speaking, high productivity consumer product injection moldingmachines include complex cooling systems (i.e., cooling systems having alevel four cooling system complexity level or higher). Level zero tolevel three cooling complexity level systems generally do not producecooling capacity that is sufficient for conventional high productivityinjection molds, which include molds made of high hardness, low thermalconductivity materials.

Advantageously, the disclosed low constant pressure injection moldsinclude cooling systems having cooling complexity levels of three orless, preferably cooling complexity level three, two, or one, whichlowers production costs and increases efficiency over conventional highpressure injection molding machines.

As used herein, a cooling complexity level zero mold assembly is definedas a mold assembly that includes no active cooling system. In otherwords, a cooling complexity level zero mold assembly is only passivelycooled through the conduction of heat through the mold sides and supportplates, and eventually to the atmosphere surrounding the mold assembly.Cooling complexity level zero mold assemblies typically have relativelylong cycle times (as it takes a significant amount of time for theplastic within the mold to freeze because of the slow cooling rate). Asa result, high productivity consumer product mold assemblies (e.g., moldassemblies used in class 101-102 molding machines) do not use coolingcomplexity level zero mold assemblies.

Turning now to FIGS. 5A-5E, different embodiments of a coolingcomplexity level one mold assembly 328 (and/or different embodiments ofa support plate in the mold assembly) are illustrated. The mold assembly328 may include a mold 370 having a first side 372 and a second side374. The first side 372 and the second side 374 form a mold cavity 376therebetween. The first side 372 may be supported by a first supportplate 378 and the second side 374 may be supported by a second supportplate 380. The first and second support plates 378, 380 may be attachedto a press (not shown), which actuates to move the first and secondsides 372, 374 during the molding process. One or more cooling lines 382may be formed in one or more of the support plates 378, 380. Because thefirst and second sides 372, 374 are made from a highly thermallyconductive material, heat flows through the first and second sides 372,374 to the support plates 378, 380 at a rate that is sufficient to coolplastic in the mold cavity 376 in an acceptable amount of time.

The support plates 378, 380 may include posts or other projections 381that extend outward, away from the support plate 378, 380, towards themold 370. The cooling lines 382 may extend into the posts 381, which canform cores for the mold 380. The posts 381 can be configured to fittogether with recesses in the mold 370, to form the mold cavities. Forexample, the projection of the embodiment of FIG. 7 can be used with thecooling lines 382, and the projection can be configured to extend insideany of the posts 381, of the embodiment of FIG. 5B. Any of the posts 381can be configured to be cylindrical, as shown in FIG. 5B, or tapered, orany other workable shape, in any convenient size, for fitting as a moldcore or mold cavity. Any of the posts 381 can be configured to partiallyor fully rest on an outer surface of the mold 380 or a mold receivingplate, or to extend into a recess or hole within an outer surface of themold 380 or a mold receiving plate.

The projection of the cooling line, the post 381, and the mold 370, inFIG. 5B, can be configured together in any workable combination eitheras a unitary structure, or as a structure of permanently connectedelements, or as a structure of interchangeable elements. As an example,a projected cooling line from FIG. 7 and a post 381 can together form aninterchangeable boss, which can be removably connected into a moldand/or a mold receiving plate, and thus be connected into cooling linesin that mold or plate. As another example, a projected cooling line fromFIG. 7 can be configured to be interchangeable with posts of varioussizes and shapes, for different molds; and when a projected cooling linecan be removably connected from such a post, this offers an additionaldegree of flexibility in the molding process, with the ability toquickly change a molding machine from one mold to another mold, withouthaving to remove the cooling line(s) and the receiving plate(s) duringthe change.

As a particular example, a post 381 and a cavity in a mold 370 can besized and positioned such that the whole geometry of the molded part canbe maintained in the mold cavity formed by the post 381. In this way,the molding surfaces of the cavity can be continuous, and no witnessline should be present on the molded part, which provides an aestheticand design benefit. Optionally, the mold cavity can be sized and/orpositioned with stackable plates to create the necessary heights for themolding surfaces and/or the mold can be configured with movable slideplates (sometimes referred to as stripper plates), mounted between thecavity and the core, which can have mechanical or hydraulic actuations.Further, this particular example can also be used with interchangeableparts, as described above.

The mold 370 may include a complementary feature so that the mold mayfit around (FIG. 5B), within (FIG. 5C), or upon (FIGS. 5D and 5E) theposts 381. In this way, the cooling lines 382 may be located closer tothe mold cavity without extending the cooling lines 382 into the mold370 or into the first and second mold sides 372, 374. As a result, thesupport plates 378, 380 may receive molds having a variety of differentmold cavity shapes. The molds may thus be formed without cooing linesintegrated into the first and/or second sides 372, 374, which reducesmanufacturing costs of the molds 370.

Conventional high output consumer product injection mold assemblies donot use cooling complexity level one mold assemblies because such moldassemblies do not adequately cool plastic with in a mold cavity formedby two high hardness, low thermal conductivity materials. Coolingcomplexity level one mold assemblies are defined as containing allactive cooling lines 382 within the support plates 378, 380, even ifmore than one machining axis is needed to form the cooling lines 382. Inthe example of FIGS. 5A-5E, the mold may be a stack mold, a cube mold, ashuttle mold, a helicopter mold, a mold having rotating platens, orother multi-cavity molds to increase productivity if desired.

Turning now to FIG. 6, a cooling complexity level two mold assembly 328is illustrated. The cooling complexity level two mold assembly 328 isidentical to the cooling complexity level one mold assembly 328 of FIG.5, with the exception that the cooling lines 382 in the embodiment ofFIG. 6 extend through at least one support plate 378, 380 and into atleast one mold side 372, 374 (i.e., as opposed to the cooling lines 382only extending through the support plates 378, 380). The cooling lines382 have terminal ends 384. However, each cooling line 382 is machinedalong an axis that is parallel to a single machining axis.

The cooling lines 382 may extend outward to form a projection whichincludes a baffle 386, as shown in more detail in FIG. 7, to facilitatecooling fluid flow through the cooling line 382. In an alternativeembodiment of FIG. 7, the baffle 386 can be replaced with a spiralcavity that extends outward through and into the projection, so coolingfluid can flow in one side of the base of the projection, through thespiral cavity, and out the other side of the base. In anotheralternative embodiment of FIG. 7, the baffle 386 can be replaced with abubbler cavity that extends outward through and into the projection, socooling fluid can flow around the inside of the projection.

Cooling complexity level two mold assemblies have not been used in highoutput consumer product injection molding machines (i.e., class 101-102injection molding machines) because cooling complexity level two moldassemblies do not have enough flexibility to machine cooling lines closeto the mold surfaces of the mold cavity and therefore, coolingcomplexity level two mold assemblies do not provide adequate cooling forconventional high output mold assemblies having high hardness, lowthermal conductivity molds.

Turning now to FIG. 8 an embodiment of a cooling complexity level threemold assembly 328 is illustrated. A cooling complexity level three moldassembly 328 is defined by cooling channels 382 having at least twodifferent machining axes. At least one cooling line 382 may include twodifferent machining axes and a terminal end. More particularly, thecooling line 382 may have a bend or turn. For example, the cooling line382 may include a first machining axis that is substantially parallel tothe opening-closing stroke S of the mold assembly 328 and a secondmachining axis that is angled with respect to the first machining axis.Like cooling complexity level two mold assemblies, cooling complexitylevel three mold assemblies have not been used in high output consumerproduct injection molding machines (e.g., class 101-102 injectionmolding machines) because level three cooling complexity does not haveenough flexibility to machine cooling lines close to the mold surfacesof the mold cavity and therefore, cooling complexity level three moldassemblies do not provide adequate cooling for conventional high outputmold assemblies having high hardness, low thermal conductivity molds.

Turning now to FIG. 9, a cooling complexity level four mold assembly 328is illustrated. The cooling complexity level four mold assembly 328includes a plurality of cooling lines 382, a first cooling line 382 ahaving a terminal end 384 and a second cooling line 382 b being athrough-bore without a terminal end. The first cooling line 382 aextends from the support plate 378 into the first mold side 372 and thesecond cooling line 382 b extends through the first mold side 372. Amachining axis for the first cooling line 382 a is different from amachining axis for the second cooling line 382 b. In other words, thecooling lines 382 have at least two different machining axes forformation. Cooling complexity level four mold assemblies have been usedin some high output consumer product injection molding machines (e.g.,class 101-102 injection molding machines) having mold assemblies withvery simple mold cavity geometries.

Turning now to FIG. 10, a cooling complexity level five mold assembly328 is illustrated. The cooling complexity level five mold assembly 328includes a first cooling line 382 that is a through-bore having twodifferent machining axes. As illustrated in FIG. 10, the first coolingline 382 includes a first section 390 and a second section 392 that areangled with respect to one another and meet at a junction or turn 394.Machining the first cooling line 382 with two different axes that mustmeet at an internal location in the mold part requires great precisionand thus more costly equipment, along with a greater manufacturing time.However, cooling complexity level five mold assemblies 328 have beenused in high output consumer product injection molding machines (e.g.,class 101-102 injection molding machines) because cooling complexitylevel five mold assemblies allow for greater customization in coolingline placement. Thus, cooling lines can be placed closer to the moldcavity than in cooling complexity mold assemblies of lesser complexity.As a result, the more complex cooling complexity mold assembly can atleast partially offset the drawback of lower thermal conductivity foundin conventional injection molds made of high hardness, low thermalconductivity materials.

Turning now to FIG. 11, a cooling complexity level six mold assembly 328is illustrated. The cooling complexity level six mold assembly 328 is acooling complexity level one to five mold assembly that also includes atleast one actively cooled dynamic molding part 398. Forming coolingchannels in a dynamic molding part 398 requires great precision.Moreover, actively cooled dynamic molding parts 398 require complicatedflow mechanisms that move with the dynamic molding part 398 duringoperation of the mold assembly 328. Cooling complexity level six moldassemblies have been used in high output consumer product injectionmolding machines (e.g., class 101-102 injection molding machines).

Turning now to FIG. 12, a cooling complexity level seven mold assembly328 is illustrated. The cooling complexity level seven mold assembly 328is a cooling complexity level two through six mold assembly thatincludes at least one conformal cooling cavity 399. The conformalcooling cavity 399 at least partially complements the contours of themold cavity to provide maximum active cooling. The conformal coolingcavity 399 is non-linear, non-coaxial, and/or non-planar. Conformalcooling cavities 399 require complex machinery to form. Additionally,conformal cooling cavities 399 take significant amounts of time to form.As a result, cooling complexity level seven mold assemblies are veryexpensive and are generally reserved for high output consumer productinjection molding machines that have very intricate part geometries.

The simplified cooling systems described herein may be incorporated intovirtually any type of conventional injection mold, such as an injectionmolding machine having a cube mold assembly 428, as illustrated in FIG.13.

Generally speaking, the low constant pressure injection molding machinesof the present disclosure include molds and/or mold assembliesmanufactured from materials having high thermal conductivity, asdiscussed above. This high thermal conductivity allows the disclosed lowconstant pressure injection molding machines, molds, and mold assembliesto cool molded parts using cooling complexity level three moldassemblies or lower for virtually any part geometry. Preferably acooling complexity level two mold assembly will be used to cool a moldedpart. More preferably a cooling complexity level one mold assembly willbe used to cool a molded part. For some part geometries, a coolingcomplexity level zero mold assembly may even be used. The coolingcomplexity level three or lower mold assemblies may be used even inultra high output consumer product injection molding machines (e.g.,class 101-102 injection molding machines) where more complex coolingsystems were needed for conventional injection molds made from highhardness, low thermal conductivity materials. As a result, the disclosedlow constant pressure injection molds and mold assemblies, and thus theinjection molding machines, are less costly to manufacture, whiledecreasing mold cycle times and increasing mold productivity due atleast in part to the availability of less complex cooling systems.

An additional benefit of molds made from high thermal conductivitymaterials is that a temperature profile for the mold is more uniformduring the injection molding process than in conventional molds. Inother words, there is less temperature variation from point to pointwithin the mold. As a result, parts manufactured in molds with highthermal conductivity have less internal stress (and a more uniformcrystalline structure) than parts manufactured in conventional molds.This lower internal stress and more uniform crystallinity result inlower rates of part warp. In conventional molds, the mold cavity isoften designed to offset part warp due to non-uniform temperaturegradients, which adds to the cost and complexity of conventional moldassemblies. Finalizing a particular offset usually requires an iterativeand time consuming trial process. In high thermal conductivity molds,the mold cavity need not be designed to offset warp because the moldedpart does not experience a significant amount of warp, as internalstresses are more uniform due to the more uniform cooling. Thus, theiterative offset process used in the design of conventional molds may beavoided, further reducing manufacturing costs and time.

Test Data

Computer analyses of several different mold configurations wereconducted to show the differences in temperature and heat flux between astandard cooling system in a conventional high hardness, low thermalconductivity mold and a simplified cooling system in a high thermalconductivity mold. The computer program used was SigmaSoft version 4.8made by Magma Corporations. The high hardness, low thermal conductivitymaterial used to model the conventional cooling system and the idealizedcooling system for each test was P20 steel. The high thermalconductivity materials used to model the simplified cooling system wereQC10 Aluminum, copper, and Mold Max®.

Example #1

In a test of a first example mold, a computer model of a rectangularmold was used. The rectangular mold was modeled under five differentconditions. First, an “ideal” condition was modeled. The ideal conditionincluded a completely conformal cooling channel located 5 mm from themolding surfaces. The ideal condition is considered to be better thanany practical cooling system in existence today and may be considered toproduce a theoretical maximum amount of cooling for the given moldcavity.

In a second condition, the ideal cooling channel was moved in thecomputer model to 7.5 mm from the mold surfaces while still remainingcompletely conformal. One skilled in the art will realize thatcompletely conformal cooling channels are practically impossible for anyshape (even very simple shapes) because if the completely conformalcooling channel were continuous in all respects the mold surfaces wouldbe completely separated from the rest of the mold by the coolingchannel.

In a third condition, the ideal cooling channel was moved in thecomputer model to 10 mm from the mold surfaces while still remainingcompletely conformal. The third condition may be considered toapproximate the best practical cooling configuration because practicalcooling channels could be machined closer than 10 mm, but would not becompletely conformal.

In a fourth condition, the ideal cooling channel was moved in thecomputer model to 12.7 mm from the mold surfaces while still remainingcompletely conformal.

In a fifth condition, a conventional cooling channel was located in thecomputer model at a distance of 5 mm from the molding surfaces. Theconventional cooling channel approximates the practical best casecooling system for a conventional mold. 5 mm is generally accepted to bea close as is practically possible for a cooling channel to be to a moldcavity surface. Closer than 5 mm would run the risk of mold deformationin the area of the cooling channel during plastic injection.

Finally, a simplified cooling system, such as one of the coolingcomplexity level zero to three mold assemblies described above, wasmodeled at 5 mm, 10 mm, and 15 mm distances in a high thermalconductivity material, such as the materials that would be used tomanufacture the molds and mold assemblies in the low constant pressureinjection molding machines described herein.

The results of the test are summarized in Table 1 below in which thex-axis represents distance from the mold surface and the y-axisrepresents heat flux.

TABLE 1 Heat Flux Rectangle 5 mm 7.5 mm 10 mm 12.7 mm 15 mm Ideal 28.1322.64 18.81 15.91 BTU/mm2 BTU/mm2 BTU/mm2 BTU/mm2 Conven- 19.05 tionalBTU/mm2 Simplified 28.98 27.52 26.12 BTU/mm2 BTU/mm2 BTU/mm2

The data summarized in Table 1 is illustrated in chart form in Chart 1below.

As is expected, heat flux drops as the cooling channel is moved fartherfrom the mold surface. However, as illustrated in Chart 1, thesimplified cooling system exceeds the heat flux of even the idealcooling system in a conventional mold at 5 mm In other words, thesimplified cooling system provides better cooling than even thetheoretical best cooling in a conventional mold. Moreover, heat fluxthrough the mold with the simplified cooling system did not drop off asfast with increasing distance from the mold surface. This feature of thesimplified cooling system allows cooling channels to be located fartherfrom the mold cavity surfaces than in conventional molds, which resultsin more uniform temperatures within the mold and fewer hot spots. Themore uniform temperature distribution within the mold leads to moreconsistent molded parts.

Similar tests were carried out for various part geometries including acircle, a square, a rectangle, and an oblong deodorant cap. The testresults are illustrated below in Tables 2-4 and Charts 2-4.

TABLE 2 Heat Flux Circle 5 mm 7.5 mm 10 mm 12.7 mm 15 mm Ideal 21.0316.71 13.85 11.66 BTU/mm2 BTU/mm2 BTU/mm2 BTU/mm2 Conventional 12.55BTU/mm2 Simplified 22.2 20.63 19.41 BTU/mm2 BTU/mm2 BTU/mm2

TABLE 3 Heat Flux Square 5 mm 7.5 mm 10 mm 12.7 mm 15 mm Ideal 20.5616.5 13.68 11.5 BTU/mm2 BTU/mm2 BTU/mm2 BTU/mm2 Conventional 14.55BTU/mm2 Simplified 23.63 22.3 21.08 BTU/mm2 BTU/mm2 BTU/mm2

TABLE 4 Heat Flux Deodorant Cap 5 mm 7.5 mm 10 mm 12.7 mm 15 mm Ideal7.04 5.63 4.65 4.07 BTU/mm2 BTU/mm2 BTU/mm2 BTU/mm2 Conventional 5.1BTU/mm2 Simplified 10.4 9.78 9.21 BTU/mm2 BTU/mm2 BTU/mm2

While the rectangle, square and circle shapes shown above are relativelysimple shapes, these shapes do not have any real practical use. Thedeodorant cap data is data from an existing injection molded part,namely a cap for a deodorant container. The deodorant cap tests modeleda mold assembly for manufacturing a Secret® deodorant cap made by TheProcter & Gamble Company as of 2007. The deodorant cap represents anexample of a relatively simple molded part geometry. The deodorant cap,while remaining a relatively simple shape, is more complex than therectangle, square, or circle examples above. When comparing the data, itis evident that the simplified cooling system described herein becomesmore effective as compared to conventional cooling systems as partgeometry becomes more complex. For example, the simplified coolingsystem is approximately twice as effective, with respect to heat flux,as the practical best conventional cooling for the deodorant cap at thesame distance from the mold cavity surface. Moreover, at 15 mm thesimplified cooing system is approximately 80% better than theconventional cooling system at 5 mm Similarly, at 5 mm, the simplifiedcooling system has approximately 47% higher heat flux than an idealizedcooling system at 5 mm In other words, heat flux through first andsecond mold sides in a simplified cooling mold is greater than heat fluxthrough first and second mold sides of an idealized cooling mold whenthe simplified cooling lines and the idealized cooling lines are formedat the same distance from the mold cavity. As a result, the simplifiedcooling system may be more easily manufactured while providing moreefficient cooling than a conventional cooling system.

The more efficient cooling provided by the simplified cooling systemsdescribed herein also results in a more uniform temperature distributionwithin the mold cavity. Using the same computer program described above(i.e., Sigma Soft v. 4.8), a test was run on the deodorant cap todetermine the temperature distribution within the mold cavity. Thecomponents included in the analysis included a moving mold side and afixed mold side. Multiple transient thermal cycles were considered tocapture a steady state mold temperature profile. In each cycle, theprogram accounted for mold closing time, a cooling phase, and a moldopening time to yield an accurate representation of the transientthermal conditions during a normal molding cycle. Upon mold closing, themold cavity was assumed to be filled with a polymer melt at a uniformmelt temperature of 218° C. The cooling lines were maintained at aconstant and uniform temperature of 20° C. The mold sides were given aninitial temperature of 30° C. at the start of the first cycle. Theanalysis was completed for a total of 16 cycles to ensure that theresults reached a quasi- steady state. The thermal heat transfercoefficients between various mold components are listed below.

Heat transfer coefficent Component 1 Component 2 W/m² K Mold fixed partMold moving part 10,000 Mold fixed and moving parts Polymer melt 800Mold fixed and moving parts Cooling fluid 10,000

The material properties used to describe the thermal properties of eachcomponent include density, heat capacity at constant pressure (cp) andthermal conductivity. The thermal properties for each component materialare summarized below.

Thermal Density Heat Capacity Conductivity Component (g/cm{circumflexover ( )}3) J/kgK W/mK P20 Steel 7.72 496 26 QC10 Aluminum 2.83 913.9160 Pure Copper 8.9 396 390 Mold Max ® XL 8.86 393.9 68.9 35 MFI PP0.748 2039 0.16 FPT350WV3

The results of the analysis were evaluated at the end of the 16^(th)cycle. The minimum and maximum temperatures on the cavity surface ofboth the moving side and the fixed side of the mold assembly wererecorded. The maximum temperature gradient on either the moving side orthe fixed side was defined as the maximum temperature minus the minimumtemperature, which provides a metric of thermal uniformity for each moldpart. The thermal gradient across the mold wall, which is defined as themaximum temperature anywhere on the fixed side minus the minimumtemperature anywhere on the moving side and the maximum temperatureanywhere on the moving side minus the minimum temperature anywhere onthe fixed side, provides an additional measure of thermal uniformity.

The results of the simulation are summarized below in Table 5.

TABLE 5 Idealized Idealized Idealized Conventional ConventionalConventional 5 mm 10 mm 15 mm 5 mm 10 mm 15 mm Fixed Side Max Temp ° C.28.7 33.3 37.4 35.4 38.9 41.7 Min Temp ° C. 24.2 26.5 28.8 27.7 30.736.2 Max Delta ° C. 4.5 6.8 8.6 7.7 8.2 5.5 Moving Side: Max Temp ° C.48.34 67 85.4 58.1 58.5 58.6 Min Temp ° C. 26.8 32.4 37.9 31 30 31.7 MaxDelta ° C. 21.54 34.6 47.5 27.1 28.5 26.9 Gradient across 24.14 40.556.6 30.4 27.8 22.4 wall ° C. Simplified Simplified SimplifiedSimplified Simplified Simplified 5 mm 5 mm 5 mm 10 mm 10 mm 10 mm QC 10Cu Mold Max QC 10 Cu Mold Max Fixed Side Max Temp ° C. 23.7 22.5 27.424.1 22.9 29.5 Min Temp ° C. 22.1 21.5 24.1 22.3 21.7 25.3 Max Delta °C. 1.6 1 3.3 1.8 1.2 4.2 Moving Side: Max Temp ° C. 37.6 30.1 53.3 38.431.7 57.9 Min Temp ° C. 26.1 24.1 28.5 26.9 24.4 29.6 Max Delta ° C.11.5 6 24.8 11.5 7.3 28.3 Gradient across 15.5 8.6 29.2 16.1 10 32.6wall ° C. Simplified Simplified Simplified 15 mm 15 mm 15 mm QC 10 CuMold Max Fixed Side Max Temp ° C. 24.8 22.7 29.9 Min Temp ° C. 22.9 21.626 Max Delta ° C. 1.9 1.1 3.9 Moving Side: Max Temp ° C. 41.6 34.3 60.9Min Temp ° C. 27.3 24.3 30.5 Max Delta ° C. 14.3 10 30.4 Gradient across18.7 12.7 34.9 wall ° C.

As illustrated above, a simulated conventional cooling system machinedto within 5 mm of the mold cavity resulted in a temperature delta of7.7° C. in a fixed side of the mold and a temperature delta of 30.4° C.in a moving side of the mold. Similarly, an idealized conventionalcooling system (as defined above) machined to within 5 mm of the moldcavity resulted in a temperature delta of 4.5° C. in the fixed side and24.14° C. in the moving side.

Conversely, a simulated simplified cooling system, as described herein,machined to within 5 mm of the mold cavity resulted in a temperaturedelta of only 1.6° C. in the fixed side and only 15.5° C. in the movingside. When machined at 10 mm from the mold cavity, the simplifiedcooling system resulted in a 1.8° C. delta in the fixed side and a 16.1°C. delta in the moving side. Finally, when machined at 15 mm from themold cavity, the simplified cooling system resulted in a 1.9° C. deltain the fixed side and a 18.7° C. delta in the moving side.

It was found that the simplified cooling system machined at 5 mm, 10 mm,or 15 mm from the mold cavity surface exhibited a temperature delta thatwas 7% less to 78% less in the fixed side and between 75% less toapproximately 41% less (in the case of QC10) temperature delta in themoving side when compared to respective mold sides in an idealizedcooling system machined at 5 mm from the mold cavity surface.

To summarize, the simplified cooing systems described herein milled at 5mm from the mold cavity reduced temperature delta in the mold cavity byas much as 78% as compared to the idealized conventional cooling at 5 mm(thus, a ratio of temperature gradients for simplified cooling toidealized conventional cooling is less than one) and by as much as 87%as compared to the conventional cooling at 5 mm in the fixed side of themold. In the moving side of the mold, the simplified cooling system at 5mm reduced temperature delta by as much as 75% as compared to theidealized conventional cooling at 5 mm (again, a ratio of temperaturegradients for simplified cooling to idealized conventional cooling isless than one) and by as much as 78% as compared to the conventionalcooling at 5 mm. Even when milled at a greater distance (e.g., 15 mm)from the mold cavity, the simplified cooling system reduced temperaturedelta by as much as 85% as compared to the conventional cooling at 5 mmin the fixed side and by as much as 63% as compared to the conventionalcooling at 5 mm in the moving side. As a result, the simplified coolingsystems described herein may be machined at greater distances from themold cavity, which reduces manufacturing costs of the mold by making themachining of the cooling channels easier, while still providing superiorcooling capability vs. conventional cooling systems. This superiorcooling capability and more uniform temperature distribution increasemold productivity while simultaneously improving part quality.

It is noted that the terms “substantially,” “about,” and“approximately,” unless otherwise specified, may be utilized herein torepresent the inherent degree of uncertainty that may be attributed toany quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue. Unless otherwise defined herein, the terms“substantially,” “about,” and “approximately” mean the quantitativecomparison, value, measurement, or other representation may fall within20% of the stated reference.

It should now be apparent that the various embodiments of the productsillustrated and described herein may be produced by a low constantpressure injection molding process. While particular reference has beenmade herein to products for containing consumer goods or consumer goodsproducts themselves, it should be apparent that the low constantpressure injection molding method discussed herein may be suitable foruse in conjunction with products for use in the consumer goods industry,the food service industry, the transportation industry, the medicalindustry, the toy industry, and the like. Moreover, one skilled in theart will recognize the teachings disclosed herein may be used in theconstruction of stack molds, multiple material molds includingrotational and core back molds, in combination with in-mold decoration,insert molding, in mold assembly, and the like.

Part, parts, or all of any of the embodiments disclosed herein can becombined with part, parts, or all of other embodiments known in the art,including those described below.

Embodiments of the present disclosure can be used with embodiments forinjection molding at low constant pressure, as disclosed in U.S. patentapplication Ser. No. 13/476,045 filed May 21, 2012, entitled “Apparatusand Method for Injection Molding at Low Constant Pressure” (applicant'scase 12127) and published as US 2012-0294963 A1, which is herebyincorporated by reference.

Embodiments of the present disclosure can be used with embodiments forpressure control, as disclosed in U.S. patent application Ser. No.13/476,047 filed May 21, 2012, entitled “Alternative Pressure Controlfor a Low Constant Pressure Injection Molding Apparatus” (applicant'scase 12128) and published as US 2012-0291885 A1, which is herebyincorporated by reference.

Embodiments of the present disclosure can be used with embodiments fornon-naturally balanced feed systems, as disclosed in U.S. patentapplication Ser. No. 13/476,073 filed May 21, 2012, entitled“Non-Naturally Balanced Feed System for an Injection Molding Apparatus”(applicant's case 12130) and published as US 2012-0292823 A1, which ishereby incorporated by reference.

Embodiments of the present disclosure can be used with embodiments forinjection molding at low, substantially constant pressure, as disclosedin U.S. patent application Ser. No. 13/476,197 filed May 21, 2012,entitled “Method for Injection Molding at Low, Substantially ConstantPressure” (applicant's case 12131Q) and published as US 2012-0295050 A1,which is hereby incorporated by reference.

Embodiments of the present disclosure can be used with embodiments forinjection molding at low, substantially constant pressure, as disclosedin U.S. patent application Ser. No. 13/476,178 filed May 21, 2012,entitled “Method for Injection Molding at Low, Substantially ConstantPressure” (applicant's case 12132Q) and published as US 2012-0295049 A1,which is hereby incorporated by reference.

Embodiments of the present disclosure can be used with embodiments forco-injection processes, as disclosed in US patent application 61/602,650filed Feb. 24, 2012, entitled “High Thermal Conductivity Co-InjectionMolding System” (applicant's case 12361P), which is hereby incorporatedby reference.

Embodiments of the present disclosure can be used with embodiments formolding with simplified cooling systems, as disclosed in U.S. patentapplication Ser. No. 13/765,428 filed February 12, 2013, entitled“Injection Mold Having a Simplified Evaporative Cooling System or aSimplified Cooling System with Exotic Cooling Fluids” (applicant's case12453M), which is hereby incorporated by reference.

Embodiments of the present disclosure can be used with embodiments formolding thinwall parts, as disclosed in U.S. patent application Ser. No.13/476,584 filed May 21, 2012, entitled “Method and Apparatus forSubstantially Constant Pressure Injection Molding of Thinwall Parts”(applicant's case 12487), which is hereby incorporated by reference.

Embodiments of the present disclosure can be used with embodiments formolding with a failsafe mechanism, as disclosed in U.S. patentapplication Ser. No. 13/672,246 filed Nov. 8, 2012, entitled “InjectionMold With Fail Safe Pressure Mechanism” (applicant's case 12657), whichis hereby incorporated by reference.

Embodiments of the present disclosure can be used with embodiments forhigh-productivity molding, as disclosed in U.S. patent application Ser.No. 13/682,456 filed Nov. 20, 2012, entitled “Method for Operating aHigh Productivity Injection Molding Machine” (applicant's case 12673R),which is hereby incorporated by reference.

Embodiments of the present disclosure can be used with embodiments formolding certain thermoplastics, as disclosed in US patent application61/728,764 filed Nov. 20, 2012, entitled “Methods of MoldingCompositions of Thermoplastic Polymer and Hydrogenated Castor Oil”(applicant's case 12674P), which is hereby incorporated by reference.

Embodiments of the present disclosure can be used with embodiments forrunner systems, as disclosed in US patent application 61/729,028 filedNov. 21, 2012, entitled “Reduced Size Runner for an Injection MoldSystem” (applicant's case 12677P), which is hereby incorporated byreference.

Embodiments of the present disclosure can be used with embodiments forcontrolling molding processes, as disclosed in U.S. Pat. No. 5,728,329issued Mar. 17, 1998, entitled “Method and Apparatus for Injecting aMolten Material into a Mold Cavity” (applicant's case 12467CC), which ishereby incorporated by reference.

Embodiments of the present disclosure can be used with embodiments forcontrolling molding processes, as disclosed in U.S. Pat. No. 5,716,561issued Feb. 10, 1998, entitled “Injection Control System” (applicant'scase 12467CR), which is hereby incorporated by reference.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A mold assembly for a high productivity injectionmolding machine, the mold assembly comprising: a first mold side,defining at least a portion of each of a plurality of mold cavities; afirst support plate connected to the first mold side; and one or morefirst cooling lines configured to remove heat from the first mold side,during an injection molding process; wherein all of the one or morefirst cooling lines for the first mold side are contained within thefirst support plate.
 2. The mold assembly of claim 1, wherein at leastone of the one or more first cooling lines has a single axis.
 3. Themold assembly of claim 1, wherein: the one or more first cooling linesincludes a plurality of cooling lines; and each of the first coolinglines has a single axis.
 4. The mold assembly of claim 3, wherein eachof the single axes is substantially parallel to a common axis.
 5. Themold assembly of claim 1, wherein: the first support plate includes asupport plate projection that extends out away from the support plateand toward the first mold; and at least one of the one or more firstcooling lines is disposed within the support plate projection.
 6. Themold assembly of claim 5, wherein the first mold side is configured tofit upon the support plate projection, when the first support plate isconnected to the first mold side.
 7. The mold assembly of claim 1,wherein: the first support plate includes a plurality of support plateprojections that each extend out away from the support plate and towardthe first mold; at least one of the first cooling lines is disposedwithin each of the support plate projections; and the first mold side isconfigured to fit around the support plate projections, when the firstsupport plate is connected to the first mold side.
 8. The mold assemblyof claim 1, wherein: the first support plate includes a plurality ofsupport plate projections that each extend out away from the supportplate and toward the first mold; at least one of the first cooling linesis disposed within each of the support plate projections; and the firstmold side is configured to fit within the support plate projections,when the first support plate is connected to the first mold side.
 9. Themold assembly of claim 5, wherein, each of the first cooling lines thatis disposed within the support plate projection is formed with thesupport plate projection as a unitary structure.
 10. The mold assemblyof claim 5, wherein, each of the first cooling lines that is disposedwithin the support plate projection is permanently connected to thesupport plate projection.
 11. The mold assembly of claim 5, wherein,each of the first cooling lines that is disposed within the supportplate projection is removably connected to the support plate projection.12. A mold assembly for a high productivity injection molding machine,the mold assembly comprising: a first mold side, defining at least aportion of each of a plurality of mold cavities; a first support plateconnected to the first mold side; and one or more first cooling linesconfigured to remove heat from the first mold side, during an injectionmolding process; wherein all of the one or more first cooling lines forthe first mold side are contained within the first support plate and thefirst mold side; and wherein at least one of the one or more firstcooling lines has a terminal end disposed in the first mold side. 13.The mold assembly of claim 12, wherein each of the one or more firstcooling lines has a single axis.
 14. The mold assembly of claim 12,wherein: the one or more first cooling lines includes a plurality ofcooling lines; and each of the first cooling lines has a single axis.15. The mold assembly of claim 14, wherein each single axis issubstantially parallel to a common axis.
 16. The mold assembly of claim12, wherein: at least one of the one or more first cooling lines has afirst axis and a second axis; the first axis is angled with respect tothe second axis; and the first axis is connected to the second axis at aturn.
 17. The mold assembly of claim 12, wherein at least one of the oneor more first cooling lines has a cooling line projection, whichincludes the terminal end disposed in the first mold side.
 18. The moldassembly of claim 17, wherein the cooling line projection includes abaffle.
 19. The mold assembly of claim 17, wherein the cooling lineprojection includes a spiral cavity.
 20. The mold assembly of claim 17,wherein the cooling line projection includes a bubbler cavity.